Caption: Gene switches, conceptual computer artwork. Switches on the arm of a chromosome, representing the process of switching specific genes on or off. Chromosomes are composed of deoxyribonucleic acid (DNA) coiled around proteins. DNA contains sections, called genes, which determine each cell's structure, function and behaviour. How often a gene is expressed (produces functional proteins) is regulated by proteins that bind to the DNA in order to activate (switch on) or repress (switch off) the gene. Some gene therapies take advantage of this by switching certain genes on or off in order to treat a genetic disorder.